Extend the description of ALTQ to call it a system which is a framework in
altq(4) to match altq(9). This makes preserving the history section as the
author of ALTQ easier in the history section, rather than calling it a framework
in the description & a system in the history.
Add a history section to altq(4) and extend the history section in altq(9)

Approved by: bcr (mentor)
MFC after: 5 days
Differential Revision: https://reviews.freebsd.org/D14774